Der Wirkungsquerschnitt für die Ionisierung derK-Schale von Kohlenstoff durch Elektronenstoß (2–30 keV)

Abstract

The K-Ionization Cross Section of Carbon by Electron Impact (2-30 keV)The K-ionization cross section of carbon by electron impact was measured detecting quantitatively the C-K X-rays emitted by thin solid targets of known mass thickness. The experimental method and the measurements are described.The measurements confirm the result of Glupe and Mehlhorn 1,2 in the absolute values, but in respect to the relative shape of the ionization function their result is somewhat different.The comparison with theory shows very good agreement with the semi-empirical calculation of Gryzinski 3. Quantummechanical theories disagree, if they describe the impact electron by plane waves. The theory of Rudge and Schwartz 4, which uses Coulomb wave fanctions for the impact electron, is in reasonably good agreement with the experiment at the lower energies; at hundred-fold threshold energy this theory is about 25 % higher.

K-Shell Ionization Cross Sections of Light Atoms Due to Electron Impact

“…1, we have plotted electron impact ionization cross sections (EIICS) versus E from threshold to 1 GeV for carbon atom. Obtained results compared along with the experimental data given by Tawara et al [22], Isaacson [23], Hink and Paschke [24], Egerton [25] and theoretical data set of Casnati et al [11], Hombourger [12], and Kim and Desclaux [26]. Present cross sections are in good accordance with the experimental data of Tawara et al [22], Isaacson [23], Hink and Paschke [24], and Egerton [25].…”

“…Obtained results compared along with the experimental data given by Tawara et al [22], Isaacson [23], Hink and Paschke [24], Egerton [25] and theoretical data set of Casnati et al [11], Hombourger [12], and Kim and Desclaux [26]. Present cross sections are in good accordance with the experimental data of Tawara et al [22], Isaacson [23], Hink and Paschke [24], and Egerton [25]. Other theoretical cross sections by Kim and Desclaux [26] is in excellent agreement with obtained results.The difference between predicted results and the data by Hombourger [12] and Casnati et al [11] are more at low energies while at high energies present results merge with them.…”

Absolute electron impactK-ionization cross sections of titanium and nickel (?50 keV)

“…Older experimental data of the K-shell ionization cross section QK are available for medium and high Z atoms at high impact energies which show satisfying agreement with theory. New experimental data for elements of low Z at low impact energies have been published by Glupe and Mehlhorn [1], Tawara et al [-2], Hink and Ziegler [3], Hink and Paschke [4]. * Parts of this work are taken from the author's dissertation, Wiirzburg 1974. In general the agreement of these data with existing theoretical approaches cannot be regarded as satisfying because there are systematic deviations which amount to 20 % with increasing tendency for decreasing impact energy.…”

What Remains to Be Done to Allow Quantitative X-Ray Microanalysis Performed with EDS to Become a True Characterization Technique?

“…Figure 8 shows R C-Cu E 0 - E 1 as a function of E 0 , with E 1 equal to 10 keV, computed with some of the experimental ionization cross sections of C and Cu shown in Figures 2 and 3 and with the model of Casnati et al (1982) and with the computations of Bote and Salvat [equations (8), (9), and (10)]. The ratio of the cross sections for carbon was obtained from a logarithmic fit of the values measured by Hink & Pashke (1971 a , 1971 b ) and by Tawara et al (1973). Two R C-Cu E 0 - E 1 ratios were computed from the ratio of cross sections of copper measured by He et al (1997) and by Llovet et al (2000).…”